The present invention relates to a light source apparatus and a projection apparatus, in particular suitable for a projector apparatus adopting DLP (Registered Trademark) method.
In prior art, projector apparatuses using a discharge lamp such as an ultra-high voltage mercury lamp as a light source are mainstream of projector apparatuses. However, such projector apparatuses have many problems in cost and usability. For example, they consume a large amount of electric power, radiate much heat and causes noises in great deal for cooling. Further, they easily deteriorate despite their expensive prices if their temperatures are not appropriately controlled by proper cooling, and their lives become short.
On the other hand, in recent years, LEDs (Light-emitting diode) having high brightness, which are solid light-emitting elements and emit light with RGB (red, green or blue) color, have widely become commercially practical. Further, it has been tried to use LEDs as a light source of projector apparatuses.
However, illumination obtained by one LED is still much lower than that of the above ultra-high voltage mercury lamps and the like. To use LEDs as a light source of projector apparatuses, it is important how much LEDs can be arranged in a small space.
FIG. 4 illustrates an example in which LEDs 11 are arranged on one end surface 10a of a light tunnel 10. In this example, seven LEDs 11 are arranged with arranging pitches A on the end surface 10a. 
A whole internal surface of the light tunnel 10 is a reflection mirror. Brightness distribution of light beams emitted from the respective LEDs 11 with a light-supplying angle α is uniformized when the light beams travel through the light tunnel 10 while being reflected by the internal wall of the light tunnel 10. Thereafter, the light beams are applied to a light-modulating element (not shown) such as a micromirror element to form a light image, and the light image is projected and displayed by a projection lens system.
As described above, if the LEDs 11 are simply arranged at regular intervals along a cross-section perpendicular to the optical path, the number of LEDs 11 which can be arranged are limited, and no sufficient illumination is obtained as a light source of a projector apparatus.
In the same manner, there are other techniques of forming a light source portion by arranging LEDs of RGB colors in an array form. For example, Jpn. Pat. Appln. KOKAI Pub. No. 2003-262795 discloses a technique of an illumination apparatus using a solid light source, for outputting a light of uniform light distribution with a simple structure. In this technique, used is an illumination panel having a structure wherein LED elements of RGB colors serving as light source are arranged in an array form on an entrance side of a rod lens having a reflective internal surface, to enhance use efficiency of light with a simple structure. However, the technique disclosed in Jpn. Pat. Appln. KOKAI Pub. No. 2003-262795 also has a structure in which a rectangular illumination panel corresponding to the size of the incident opening of the rod lens 20 uniformizing the brightness distribution by arranging LEDs of RGB colors in an array form. Therefore, the size of the available panel is equal to the opening size of the rod lens 20, and thus the number of LEDs which can be arranged is also limited.
With respect to this point, it is possible to arrange more LEDs and form a brighter light source apparatus, by arranging LEDs in a three-dimensional manner, not on one plane.
FIG. 5 illustrates a cross-sectional structure of a light source apparatus in which an opening in a lower base surface of a housing 20 having a (rectangular) prismoidal shape is used as an outgoing surface. The whole internal surface of the upper base and the whole internal surfaces of the inclined surfaces are total reflection mirrors. As shown in FIG. 5, a large number of LEDs 21 are arranged on the external surfaces of the inclined surfaces. Light beams emitted from the LEDs 21 are introduced into the housing 20 through through-holes formed in the inclined surfaces. Then, the lights outgo from the lower base surface of the housing 20 directly, or after reflected once by the internal surface of the opposing inclined surface. The irradiation ranges of the respective light beams are shown in FIG. 5.
However, the LEDs 21 provide emitted light beams to the inside of the housing 20 through through-holes formed in the inclined surfaces of the housing 20. Therefore, as shown by arrows L in FIG. 5, a part of the light beams outgoes outside the housing 20 through the through-holes for other LEDs 21 located on a part of the opposing inclined surface closer to the opening of the lower base surface, and does not serve as illumination light effective for projection.
Although the above structure enables arranging a large number of LEDs 21 which can provide a sufficient amount of light by devising the shape of the housing 20, a part of the outgoing light is leaked to the outside of the housing 20, and thus the generated light is wasted.